U.S. patent number 5,017,116 [Application Number 07/442,499] was granted by the patent office on 1991-05-21 for spinning pack for wet spinning bicomponent filaments.
This patent grant is currently assigned to Monsanto Company. Invention is credited to Don E. Carter, Arnold L. McPeters, Hobson L. Skeen.
United States Patent |
5,017,116 |
Carter , et al. |
May 21, 1991 |
Spinning pack for wet spinning bicomponent filaments
Abstract
A spinning pack for wet spinning a tow having at least 20,000
bicomponent acrylic filaments is described. The pack includes a
plurality of specially designed plates arranged so as to provide
filaments having a substantially uniform distribution of the
components along the entire length of each filament and from
filament to filament.
Inventors: |
Carter; Don E. (St. Louis,
MO), McPeters; Arnold L. (Raleigh, NC), Skeen; Hobson
L. (High Point, NC) |
Assignee: |
Monsanto Company (St. Louis,
MO)
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Family
ID: |
26967033 |
Appl.
No.: |
07/442,499 |
Filed: |
November 27, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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291891 |
Dec 29, 1988 |
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Current U.S.
Class: |
425/131.5;
425/DIG.217; 425/382.2; 264/172.14; 264/172.16; 264/172.15;
425/192S; 425/463 |
Current CPC
Class: |
D01D
5/06 (20130101); D01F 8/08 (20130101); D01D
5/30 (20130101); D01D 4/06 (20130101); Y10S
425/217 (20130101) |
Current International
Class: |
D01D
5/30 (20060101); B29C 047/30 () |
Field of
Search: |
;425/131.5,131.1,191.1,192,192.5,382.2,463,DIG.217 ;264/171 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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41-17927 |
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Oct 1966 |
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JP |
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42-18562 |
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Feb 1967 |
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JP |
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47-38884 |
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Oct 1972 |
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JP |
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Primary Examiner: Woo; Jay H.
Assistant Examiner: Nguyen; Khanh P.
Attorney, Agent or Firm: Whisler; John W.
Parent Case Text
This is a continuation of application Ser. No. 291,891, filed Dec.
29, 1988 now abandoned.
Claims
We claim:
1. A rectangular spinning pack for wet spinning bicomponent acrylic
filaments comprising thin metal rectangular plates arranged side by
side, said plates comprising:
a. a pair of end plates
b. a plurality of first and second spacer plates, each having a
central cavity and an opening in the top edge thereof leading to
said central cavity, said central cavity being a distance X from
the bottom edge thereof;
c. a plurality of capillary plates, each having a plurality of
slots extending inwardly from the bottom edge thereof a distance
greater than said distance X; and
d. a plurality of divider plates, each having slots corresponding
in number and shape to the slots of said first and second capillary
plates except that the slots extend inwardly from the bottom edge
thereof a distance less than said distance X;
said spacer, capillary and divider plates being arranged between
said pair of end plates such that the order thereof is first spacer
plate, capillary plate, divider plate, capillary plate and second
spacer plate, whereby said slots in said capillary and divider
plates define orifices, means for forcing a first acrylic polymer
solution through said orifices via said openings and said cavities
in said first spacer plates and means for forcing a second acrylic
polymer solution through said orifices via said openings and said
cavities in said second spacer plates.
2. The pack of claim 1 fitted with a spinneret plate having an
orifice inline with each slot of each divider plate.
3. The pack of claim 2 wherein said plates are made of stainless
steel.
4. The pack of claim 3 wherein said pack has at least 20,000
orifices.
Description
BACKGROUND OF THE INVENTION
This invention relates to a spinning pack for wet spinning a large
number of bicomponent filaments, particularly, bicomponent acrylic
filaments and, more particularly, bicomponent acrylic filaments
having the specific ability to develop a helical crimp on hot or
hot/wet treatment because of a difference in shrinkage between the
two components. (Bicomponent filaments having this ability are
commonly referred to as "conjugate filaments".) The term
"bicomponent filaments", as used herein, means filaments consisting
of two components arranged either in a side-by-side or sheath/core
configuration along the length of the filaments. The term "wet
spinning" as used herein means a process in which a solution of
fiber-forming polymer is extruded from a spinning pack through
orifices directly into a liquid coagulation medium where the
polymer is coagulated to form filaments that are further processed.
Preferably, the spinning pack is immersed in the liquid coagulation
medium. However, if desired, the spinneret may be placed a short
distance (e.g. 0.5 to 2 cm) above the surface of the liquid
medium.
Spinning packs useful for wet spinning bicomponent filaments are
described in the prior art, for example, U.S. Pat. No. 3,176,345
describes a spinning pack consisting of stacked plates that are
bolted together. Some of the plates have slots defining orifices
and the remaining plates have hollow regions defining manifolds.
The plates are arranged so that a slotted plate is sandwiched
between two manifold plates. In operation of the pack two solutions
under pressure are fed to the pack, one polymer spinning solution
flows to the manifold plates on one side of the slotted plates and
the other polymer solution flows to the manifold plates on the
other side of the slotted plates. The two solutions combine in each
of the slots of the slotted plates and are extruded from each slot
as a single stream which, when coagulated, provides a bicomponent
filament. One problem encountered in using this pack is that the
distribution of the two components in the filaments is not uniform
because the lower viscosity solution tends to wrap around the
higher viscosity solution.
SUMMARY OF THE INVENTION
The present invention provides a spinning pack useful for wet
spinning bicomponent filaments. The pack is characterized in being
capable of providing a large number of conjugate filaments having a
substantially uniform distribution of the components along the
entire length of each filament and from filament to filament. The
pack comprises a plurality of assembled metal plates which define
openings through which two spinning dopes flow enroute to a
spinneret. The pack of the present invention is particularly useful
for wet spinning a tow consisting of in excess of 20,000 conjugate
acrylic filaments. The tow can then be processed into yarn useful
for applications where high bulk is desirable, for example, craft
yarns and sweater yarns.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a preferred spin pack of the invention.
FIG. 2 is a front elevation of the spin pack shown in FIG. 1.
FIG. 3 is a right side elevation of plate 21 shown in FIG. 1.
FIG. 4 is a right side elevation of plate 24 shown in FIG. 2.
FIG. 5 is a right side elevation of plate 22 shown in FIG. 2.
FIG. 6 is a right side elevation of plate 23 shown in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Spinning packs of the invention comprise individual thin metal
plates. Typically, there are four different types of thin plates
plus two end plates and a spinneret plate. The packs are provided
by first making the required number of each type of plate,
preferably, from stainless steel. These plates can be made, for
example, by machining stacks of solid plates by the technique of
electron discharge machining (sometimes referred to as wire
cutting) or by photoetching. The plates are then assembled in the
proper order and converted by appropriate means to a structure that
does not leak under conditions normally encountered in wet spinning
processes. Preferably, the structure is converted to a monolithic
structure by utilizing the process generally known as diffusion
bonding (sometimes referred to as isostatic pressing). In diffusion
bonding the assembled plates are cleaned and held together in an
inert atmosphere or under vacuum while being heated under
conditions sufficient to cause the atoms of the adjacent metal
plates to diffuse rapidly between the plates and convert the
assembled plates to a monolithic structure. For example, diffusion
bonding of stainless steel plates is accomplished by holding the
plates by pressures in the range of 50 to 2000 psig while heating
the plates at a temperature in the range of 1700.degree. to
1900.degree. F. for a period ranging from 1/2 hour to 24 hours. It
is contemplated that the plates, instead of being made from
stainless steel, may be made from other metals or from materials
such as ceramics or carbon.
A preferred spinning pack of the invention and its component parts
are shown in the accompanying Figures. Referring to FIG. 2,
spinning pack 5 consists of end walls or plates 20, spacer plates
21 and 24, capillary plates 22, divider plates 23 and spinneret
plate 25 arranged as shown in FIG. 2. As shown in FIGS. 3 and 4,
each of the spacer plates 21 and 24 has inlets 41 and 44,
respectively, leading to central cavity 50. As shown in FIG. 5,
each of the capillary plates 22 has rectangular slots 60 extending
inwardly and perpendicularly from the lower edge thereof a selected
distance. As shown in FIG. 6, each of the divider plates 23 has
rectangular slots 70 extending inwardly and perpendicularly from
the lower edge thereof. Slots 60 are of the same width as slots 70
but are longer. When plates 22 and 23 are arranged as shown in FIG.
2, slots 70 are aligned with slots 60. Spacer plates 21 differ from
spacer plates 24 in that inlet 41 of plates 21 is reversed from
inlet 44 of plates 24 as shown in FIG. 1. Spinneret plate 25 has
orifices 80 and facilitates formation of uniform filaments.
Spinneret plate 25 may be attached to the other plates by any
suitable means. According to a preferred embodiment of the
invention spinneret plate 25 is compression fitted (stretched) over
the other plates. According to this embodiment, plates 20-24 are
constructed and arranged so as to define a curved (convex) lower
surface over which spinneret plate 25 is stretched. Stretching of
spinneret plate 25 over plates 20-24 may be accomplished by
suitable mechanical means, such as clamps, which pull spinneret
plate 25 over the other plates. The convex surface defined by
plates 20-24 conforms to and fits snugly against the upper surface
of spinneret plate 25. (If the lower surface formed by plates 20-24
were flat instead of convex, spinneret plate 25 tends to bulge away
and separate from the other during use of the pack.) Slots 70 of
plates 23 align with orifices 80 of spinneret plate 25 and
compensate for any misalignment of slots 60 and orifices 80. If
desired, however, slots 70 may be omitted (i.e. plates 23 may be
solid).
According to another embodiment of the invention, spinneret plate
25 is omitted from pack 5, plates 23 have slots 70 and the lower
surface of the pack defined by plates 20-24 is flat. (In this
instance, if plates 23 were solid, each pair of opposite slots 60
abutting plates 23 would form two monocomponent fibers instead of
one bicomponent fiber.)
Referring to FIGS. 1 and 2, in operation of pack 5, utilizing
spinneret plate 25 and slots 70, two polymer solutions (i.e. dopes)
are individually and separately fed under pressure by means of
manifolds (not shown) to openings 41 and 44, one solution to
openings 41 and the other solution to openings 44. The solutions
flow from openings 41 and 44 into cavities 50. From cavities 50 the
solution flow through slots 60 and combine or join in slots 70. The
combined solutions flow through slots 70 and are extruded as
streams from spinneret plate orifices 80. Slots 60 and 70 and
orifices 80 are carefully sized so that the pressure drop of each
spin dope when flowing through orifices 80 at the desired rate is,
preferably, in the range of 20 to 200 psig. This permits each
orifice 80 to deliver an accurately controlled flow of dope to its
outlet. The solutions are emitted from orifices 80 in the form of
streams which, when coagulated, provide bicomponent filaments in
which the components are arranged in either a side-by-side or
sheath/core configuration along the longitudinal axis of the
filaments, depending on the viscosities of the two spinning
solutions. In general, when the solutions are of the same
viscosity, the components will be arranged in a side-by-side
configuration, whereas if solutions are each of a different
viscosity, the components will be arranged in or approximate a
sheath/core configuration since the lower viscosity solution tends
to wrap around the higher viscosity solution. According to one
embodiment of spinning pack 5 improved distribution of flow is
achieved by sizing the thickness and width of slots 60 so that
those through which one of the two spinning dopes flows enroute to
orifices 80 are of a lesser cross-sectional area than those through
which the other spinning dope flows. According to another
embodiment of the invention, formation of sheath/core fibers is
facilitated by placing tubes between each opening defined by slots
60 and 70 and each spinneret plate orifice 80. The tubes are, for
example, 2.54 cm long and sealably connected to each said opening
and its corresponding orifice 80.
During operation of pack 5, the dopes are considerably hotter
(30.degree. to 60.degree. C.) than the aqueous coagulating liquid.
It is important that dope in cavities 50 located at the outer
portion of the pack is not cooled by the aqueous coagulating liquid
to a greater extent than is dope in cavities 50 located at the
center of the pack. Lowering the temperature of the dope, increases
its viscosity, lowers its flow rate through the pack and,
consequently, causes smaller diameter fibers to be formed. To
prevent this, it is a conventional practice to heat packs, for
example, by jacketing the pack and circulating a heating fluid
(e.g. steam or oil) in the jacket or by providing channels in the
plates for circulating a heated fluid.
For purposes of providing conjugate type filaments having the
ability to develop the highest possible level of bulk, the
components are arranged in a side-by-side configuration where the
distribution of the components is in a ratio of 1:1, that is in
cross-section one half of the filament consist entirely of one of
the components and the other half consists entirely of the other
component. The distribution of the components in the filaments can
be selected by selecting the appropriate rates at which the
solutions are fed to the orifices, for example, if one of the
solutions is fed to the orifices at twice the rate of the other
solution, the distribution of the two components in the filament
will be in a ratio of 1:2, assuming Newtonium flow and other
conditions remained the same. The distribution of the components in
each filament and from filament to filament is maintained
substantially the same by means of divider plates 23.
The packs of the invention are particularly useful for providing a
tow consisting of at least 20,000 conjugate acrylic filaments in
which the distribution of the components is 1:1. Since the size of
each of the filaments formed by the pack will be determined by the
cross-sectional area of orifices 80, plates 22 and 23 must be thin
and the slots narrow in order to provide packs capable of spinning
20,000 plus filaments. Suitable plates for preparing such a pack
would be, for example, divider plates 23 each having a thickness of
3 mils, capillary plates 22 each having a thickness of 6 mils and
spacer plates 21 and 24 each having a thickness of 31 mils. (A
typical spinneret plate 25 has a thickness of 0.152 cm and each
orifice 80 a diameter of 0.009 cm.) Slots 60 and 70 are preferably
provided in plates 22 and 23 by means of electron discharge
machining techniques. The plates are assembled in the order shown
in FIG. 2. This order of assembly is continued until a pack with
the desired number of orifices is achieved. The plates are held in
alignment by means of dowel rods 28 during assembly and bonding of
the plates. The assembled pack is then preferably subjected to
appropriate diffusion bonding conditions to provide a monolithic
structure.
The following example is given to further illustrate the invention.
In the example percentages are weight percentages.
EXAMPLE
This example illustrates wet spinning conjugate acrylic filaments
using the pack of the present invention.
A first spinning solution is prepared by dissolving an appropriate
amount of an acrylic polymer containing 92.5% of acrylonitrile (AN)
and 7.5% vinyl acetate (VA) in dimethylacetamide (DMAc) to provide
a solution containing 25% of the polymer. A second spinning
solution of about the same viscosity is prepared in the same way,
except in this instance the acrylic polymer contains 92.1% AN, 7.3%
VA and 0.6% sodium p-sulfophenylmethallyl ether (SPME). For
spinning, a pack shown in the accompanying Figures and having
30,000 orifices is used. The pack is immersed in a coagulation bath
consisting of a 55% aqueous solution of DMAc at a temperature of
45.degree. C. The first solution at 100.degree. C. is fed into the
pack through inlets 41 (FIG. 1) and the second spinning solution at
100.degree. C. is fed into the pack through inlets 44 (FIG. 1). The
resulting tow consisting of 30,000 bicomponent filaments in which
the components are arranged in a side-by-side configuration is
withdrawn from the coagulation bath at a linear speed of 20 fpm
(6.1 mpm) with a theoretical jet stretch of 0.9 times by a first
set of rolls, washed on these rolls, then stretched 6 times in
boiling water between the first set of rolls and a second set of
rolls, washed on the second set of rolls, dried on drying rolls and
collected on a winder bobbin at a speed of 120 fpm (36.6 m). The
tow is then crimped and annealed with steam under conditions that
do not develop the latent helical crimp present in the conjugate
filaments of the tow. The tow is then converted to staple and made
into skeins of yarn. The yarn is then wet-dyed and dried under
conditions that develop the latent helical crimp. The resulting
yarns have excellent bulk when observed under a microscope, the
distribution of the tow components is substantially uniform along
the length of each filament and from filament to filament and there
is no visual evidence of splitting of the components.
In related experiments bicomponent filaments in which the
components are arranged in a sheath/core configuration are made by
utilizing the above dopes except in this instance the dopes are
prepared so that the dope containing SPME is of a lesser viscosity
(e.g. 1/6th) than the other dope. Similar results are obtained.
* * * * *